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Date: Tue, 06 May 2008 00:21:02 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: Re: [Xenomai-help] Loosing serial interrupt
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To: Tomas Kalibera <kalibera@domain.hid>
Cc: xenomai@xenomai.org

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Tomas Kalibera wrote:
> Hi,
>=20
> I am having problems with lost serial interrupts. Could you please
> explain to me why this happens ? I am probably missing something
> regarding scheduling in Xenomai...
> I prepared a program that triggers the problem, at least on my system.
>=20
> Thanks,
>=20
> Tomas
>=20
> The program works on my system as follows:
>=20
> 1. I run the program, it prints
>=20
> In interrupt, LStatus: 96
> In interrupt, read char, LStatus: 96
>=20
> [which means that it received a serial interrupt, because the
> transmitter receiver is empty]
>=20
> 2. I send a single character to the program over serial line
>=20
> 3. the program wakes up (10 seconds after (1))
>=20
> 4. the program prints
>=20
> I-NFO irq=3D4 hits=3D1
> PIC-ISR:0 PIC-IRR:0 PIC-IMR:128 UART-IIR:4 UART-LSR:97 UART-MSR:176
>=20
> [which means the interrupt at Xenomai level hit only once, although it
> should have twice, second time because of the received character
>  these too lines that repeat indefinitely, the interrupt not coming.
> although interrupts are enabled at PIC level]
>=20
> I use the "XT-PIC-XT" (8259A) interrupt controller. As far as I know,
> Linux sets up the controller to "edge triggering", but uses
> "handle_level_irq" for it. When received by Xenomai, the interrupt is
> masked and acked at PIC level ( "ack" means EOI at 8259A). When the
> interrupt handling in the program finishes, it unmasks the interrupt. I=

> verified  that my 8259A has a latch that can detect the UART interrupt
> even if masked, so that when unmasked again, it can be delivered.

Try to pass I_EDGE to rt_intr_create. The UART IRQs are edge-triggered,
so you have to enable the appropriate handling at kernel IRQ handler leve=
l.

Jan


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